1. Field of the Invention
The present invention relates generally to fluid pumps. More particularly, the invention concerns a fluid pump for precisely controlling the transfer of medicaments and other beneficial agents from a source of fluid to a patient.
2. Discussion of the Prior Art
A number of approaches have been suggested in the past for delivering fluid medicaments and other beneficial agents to a patient. The most common apparatus for this purpose is the so-called "gravity feed system". This system involves the use of a flexible bag that is supported above the patient and contains the fluid to be delivered. The fluid is delivered to the patient by force of gravity via a flexible tube that extends between the bag and the patient. The rate of fluid flow to the patient from the bag is basically a function of the amount of restriction of the tube leading to the patient.
To more precisely and reliably control the rate of fluid flow to the patient, several types of devices have been proposed. These devices are generally either mechanical or electronic. Exemplary of one prior art mechanical type delivery device is that described in U. S. Pat. No. 3,464,359 issued to King et al. The King et al device comprises a fluid pump for moving fluid from one system to another under pressure and includes means to assert positive control over the flow rate and also to isolate the outlet of the pump from small quantities of air occurring therein. The device basically comprises a pump body having a central chamber provided with an inlet and an outlet port. Pistons are associated with each port and are movable within the central chamber between a port open and port closed positions. The pistons are constructed and arranged so as to move fluid from one system, through the inlet port of the pump, to the central pump chamber of the pump, toward the outlet port of the pump and then into the second system.
Another prior art mechanical pumping device is disclosed in U.S. Pat. No. 5,163,822 issued to Koelln. The Koelln device comprises a radial piston pump having a pump body with two pump chambers disposed in a straight line. Pistons reciprocate within the pump chambers and are coupled to an actuator that is rotatable about an axis which bisects the straight line and functions to reciprocate the pistons in opposite directions. Each pump chamber is connected to an intake fluid duct and a discharge fluid duct. The inlet ducts are connected to a common main intake duct and the discharge fluid ducts are connected to a common main discharge duct. The actuator controls the operating components of the apparatus and cooperates with the valves thereof, which function to open and close the valve ducts.
In addition to mechanical type pumping devices, a number of different types of micro processor controlled, electronic pumps have been proposed for the controlled delivery of various medicaments to a patient. Exemplary of one prior art pump of this type is that described in U. S. Pat. No. 5,069,668 issued to Boydman. The pump there described is of a character that is capable of receiving a wide variety of commands as by pushing buttons or other controls in conjunction with viewing a changing display of information that is presented on a screen and of carrying out the entered commands as by causing the pumping mechanism to dispense a series of carefully timed, precisely determined quantities of liquid medicine from a reservoir. As a general rule, electronic pumps tend to be complex and are usually quite expensive.
The thrust of the present invention is to provide an elegantly simple fluid pump suitable for the reliable transfer to a patient of liquids such as intravenous solutions and liquid medicaments at precisely controlled flow rates.